Good idea is to post on forums and comment on blogs, share your links on community related websites. Hope this will help.
how do we know the forum using no follow link? can we check on the forum or any special matter to check?
In answer to does it help. YES! If done the right way and you follow the individual forum rules. I do not know about a service...I know they're out there but I enjoy using the forums personally. Helps me with tips and I pick up ideas for content on my site. Blessings!
Try to find high PR forums and it will count as a good link. Make sure it does not have the "no follow" tag otherwise it wont count.
Many blogs and forums use "nofollow" links, and remember links are supposed to be from relevant content, so it would have to be from a forum related to your site.